ABSTRACT
To achieve high-accuracy urine specific gravity discrimination and guide the design of four-waveband multispectral sensors. A modified combination strategy was attempted to be proposed based on the successive projections algorithm (SPA) and the spectral index (SI) in the present study. First, the SPA was used to select four spectral variables in the full spectra. Second, the four spectral variables were mathematically transformed by SI to obtain SI values. Then, SPA gradually fusions the SI values and establishes models to identify USG. The results showed that the SPA can screen out the four characteristic wavelengths related to the measured sample attributes. SIs can be used to improve the performance of constructed prediction models. The best model only involves four spectral variables and 1 SI value, with high accuracy (91.62%), sensitivity (0.9051), and specificity (0.9667). The results reveal that m-SPA-SI can effectively distinguish USG and provide design guidance for 4-wavelength multispectral sensors.
Subject(s)
Algorithms , Spectroscopy, Near-Infrared , Spectroscopy, Near-Infrared/methods , Least-Squares Analysis , Specific GravityABSTRACT
Copper ion (Cu2+) plays an important role in the human body because it is beneficial for metabolism. However, an excessive or slight amount of Cu2+ can cause various symptoms. Therefore, it is necessary for human health to realize the trace and visual detection of Cu2+. Referring to traditional fluorescence test papers, the qualitative and semi-quantitative detection of Cu2+ could be realized by a dual-carbon dots (CDs) ratiometric fluorescent paper-based sensor with the advantages of environmental protection, portability and low cost. In this paper, the inkjet-printed test paper with the best mixing ratio of the two CDs has been researched to maximize the spectral energy transfer of ion detection (maximum color gamut expansion). Among them, the preparation method of b-CDs has been improved, increasing the photoluminescence quantum yield (PLQY) to 88.9%. The sensitivity detection limit of the double emission ratio sensor was 0.15 nM in solution, and the human eye can distinguish at least 3 µmol L-1 Cu2+ in the paper-based sensor. Compared with the traditional single-emission sensor, the human eye was more sensitive to the color change of the emission ratio sensor. The results indicate that we not only realized the micro detection of Cu2+ with convenient methods, but also provided a promising strategy for the visual detection of Cu2+.